| Objective: It is a troublesome problem to orthopedists whether the combination of two different materials, stainless steel (SST) and Ti-6AL-4V(Ti) alloy , can fix fracture or not. In this study, the different combinations of plates and screws made of SST or Ti alloy were used to fix fractured bone. Their influences on the reactions of the surrounding tissues as well as on the healing of fracture were observed. Experimental evidences were provided for orthopedists to use SST and Ti alloy fix fracture reasonably.Methods: The experimental New Zealand rabbits with tibia fracture were randomly divided into four groups: A, B, C and D. They were fixed with the different combinations of plates and screws made of stainless steel or Ti-6AL-4V respectively: group A with the combination of Ti plates and Ti screws; group B with the combination of SST plates and SST screws; group C with the combination of Ti plates and SST screws; and group D with the combination of SST plates and Ti screws. Each two rabbits were killed at 2, 4,8,12 weeks postoperatively. 1)histology examinations: Histological sections stained with hematoxylin and eosin(HE) were examined. The quantities of inflammatory cell infiltration and fibrous capsule thickness around implanted materials were measured by an image analysis system.2)immunohistochemistry study: SABC immunohistology was performed. Monoclonal antibodies for PCNA(proliferating cell nuclear antigen) were used to detect the positive cells. Proliferation index was generated based on the number of positive-staining cells per total number of cells in a high-power field (HPF).3)Radiographical observation: At 2, 4, 8, 12 weeks after operation, X-ray was used to evaluate the healing of fracture fixed by different combinations.Results: 1)histology examinations : With an analysis of the quantity of inflammatory cells and the thickness of fibrous capsule, it shows that after 2 weeks of the operation, there were no significant differences among the four groups (P>0.05).After 4, 8, 12 weeks of the operation, there were significant differences between group A, C and group B, D; (P<0.05) but there were no significant differences between group A and C and between group B and D. 2)immunohistochemistry study : From an analysis of the proliferation index of PCNA, it shows that after 2 weeks of the operation, there were no significant differences among four groups(P>0.05). After 4, 8, 12 weeks of the operation, there were significant differences between group A, C and group B, D; (P<0.05) but there were no significant differences between group A and C and between group B and D. 3)Radiographic observation: After 2, 4, 8, 12 weeks of the operation, the radiographs of the fractures show that the different combinations of internal fixation materials do not have an obvious influence on the healing of the rabbits'fractures.Conclusion: The combining application of stainless-steel and titanium alloy in the internal fixation of rabbits'fractures does not cause serious tissue reactions and does not affect the healing within 12 weeks after the operation. |
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